textproduct: Rapid City

KEY MESSAGES

- A few severe thunderstorms are possible this afternoon especially east of Oglala Lakota County and south of I-90; damaging winds and large hail could occur.

- Cooler today, then above average temperatures (10F+ above normal) for the latter half of the week.

- Near-critical to critical fire weather conditions expected Wednesday through at least Friday.

UPDATE

Issued at 945 PM MDT Mon Aug 31 2026

Going forecast in good shape. Water vapour loop depicted shortwave over UT, which will slip northeast overnight into Tuesday bringing modest 800-600mb theta-e advection and a slug of moisture. Result will be a cluster of shra/TS through midday and then isolated strong/severe thunderstorms over south-central SD Tuesday afternoon. Temperatures will be tricky Tuesday given precipitation/cloud cover, so stuck with guidance. Then, very warm to hot and mostly dry into next weekend.

DISCUSSION

(This Evening Through Monday) Issued at 100 PM MDT Mon Aug 31 2026

Water vapor imagery shows upper low centered over eastern Saskatchewan and western Manitoba with southwest flow across the western half of the country. Shortwave trough and mid- level moisture plume is evident over the Four Corners region. Surface low pressure is centered over southeastern Saskatchewan with a cold front stretching from northern MN through western IA.

Cooler today (80s-90 on the plains with 70s to near 80 in the Black Hills) and dry with elevated fire weather the main concern. Water vapor imagery highlights upper level moisture pushing into the southern forecast area ahead of the shortwave trough to our southwest. This wave will bring showers and storms to the area late tonight/early Tuesday morning through Tuesday afternoon. While widespread severe weather is not expected, a few strong to severe storms are possible across south-central SD into south- eastern SD Tuesday.

Upper level ridge will build across the Northern Plains Wednesday through the end of the week with much hotter and drier weather. Highs will push into the 90s to near 100 by Friday (on the plains). Stronger southerly winds will develop during this time, resulting in near-critical to critical fire weather conditions Wednesday through at least Friday.

AVIATION

(For the 12Z TAFS Through 12Z Wednesday Morning) Issued At 532 AM MDT Tue Sep 1 2026

A band of showers, light rain, and embedded thunder will push across the region from southwest to northeast generally between 11z/5am and 21z/3pm today. Guidance pretty universally supports cigs/vsbys remaining VFR with this activity, although transient MVFR conditions can't be ruled out, and we're watching upstream surface observations closely in case the forecast needs to be trended up or down. Slight tweaks were made to precip timing and vsbys at KGCC and KRAP based on both high-res guidance and current radar trends. This afternoon, our attention turns to isolated thunderstorms, with the greatest coverage and severity generally east of Oglala Lakota County and south of I-90 where a few cells may become severe and produce damaging winds and large hail. A few gusts over 75 MPH and hail larger than eggs could occur in this area, along with cig/vsby drops to IFR underneath cores. This activity should end by about 02z/8pm returning us to dry VFR conditions for the night, although low-level moisture will be higher than recent days east of the Black Hills. Confidence is low, but it's not out of the question that some fog/mist/low stratus could try to develop somewhere over the plains, as hinted at in HRRR guidance. We'll continue to evaluate this potential in future forecast updates.

FIRE WEATHER

Issued At 100 PM MDT Mon Aug 31 2026

Elevated fire weather conditions today across the area with daytime RH falling into the teens, although winds will generally remain below critical levels. Precipitation chances return for southern into south-central SD late tonight into Tuesday ahead of much warmer weather to end the week.

Temperatures will warm into the upper 80s to low 90s Wednesday with even hotter temperatures Thursday and Friday as RH falls into the teens; near single digit RH possible across portions of far SW South Dakota into NE Wyoming Thursday and Friday where south-southwest winds will gust 25 to 30 mph.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.